Ethan Erhahon, Ryan Hardie and John McAtee have joined Jayden Nelson on the injured list, leaving Steven Schumacher with limited options heading into a run of three games in seven days.
Midfielder Erhahon picked up a thigh strain in the second half of the 5-1 defeat against Middlesbrough and is likely to be out until after the international break.
McAtee missed training on Thursday with a knee problem, which is as yet undiagnosed.
Hardie, who has yet to start a game for the Whites since he signed on loan from Wrexham, pulled up with a hamstring injury during an Under-21s game against Huddersfield Town and could be out of commission for a number of weeks.
On the upside, Chris Forino has suffered no further problems after making his return from a groin injury for the 21s and could be part of the squad.
Schumacher explained at his pre-Bristol City press conference: “Ryan pulled his hamstring in the Under-21s game. He has an issue from Tuesday, so we’ve had him scanned. He’s got some damage in his hamstring.
“I don’t know exactly how long it’ll be, but it’ll be a little while, which is devastating for him. Every time he feels as though he’s right there sprinting at full speed, he’s breaking down, which is bad news for him and disappointing for us, so that’s an issue.
“John McAtee didn’t train today. He has a knee issue that’s going on. We don’t know what exactly is the cause of it, but he didn’t manage to do anything today, so we don’t know whether he’ll be available. Jayden obviously not fit.
“Ethan is going to be out for a while. He’s pulled his thigh, which is disappointing. We’ll be a bit thin squad-wise, but we’ll deal with it as best as we can.”
Schumacher maintains the absences open up opportunities for others – and with Erhahon unavailable the likes of Xavier Simons or Atsuki Ito could come into midfield alongside Josh Sheehan.
“That’s it, that’s the test, that’s the challenge, that’s what you get paid for,” he added.
“Come in every day and do your best and you get a chance to play in the first team and compete for points, give it your all. That’s the beauty of this game, it can change quick. We’ve had a couple of injuries this week that were unexpected and the door might open for one or two to really stake a claim.”